There has been substantial work directed to procedures by which polluted water may be purified by the removal of halogenated organic components. Some of these processes involve the use of various types of microorganisms. For example, U.S. Pat. No. 4,401,569 to Jhaveri et al discloses methods and apparatus for treating ground water contaminated with halogenated hydrocarbon compounds. The process involves degradation of the halogenated hydrocarbons by a microorganism. In this process, growth of microorganisms is enhanced under controlled conditions by addition of nutrients and gases such as oxygen, nitrogen, carbon dioxide or a combination. Treated water carrying these microorganisms, nutrients and gases is then returned for recirculation through a contaminated area of ground to leach out and biodegrade contaminants deposited in the ground. This patent is primarily concerned with removal of hydrocarbons from contaminated ground and ground water. The Jhaveri process uses the hydrocarbon as the feed stock; that is, the hydrocarbon provides the carbon and energy to support the growth of the active microorganisms. The only compounds which will support the growth of microorganism in this process are those that are capable of serving as a sole carbon and energy source.
U.S. Pat. No. 3,979,283 to Prudom discloses a process for the microbial degradation of DDT (dichlorodiphenyl-trichloroethane) by contact with microorganisms. However, the work in this patent is limited to aromatic halogenated hydrocarbons which are degraded with the non-pathogenic, hydrocarbon utilizing strains of Nocardia, Candida and Penicillium species. A similar disclosure may be found in U.S. Pat. No. 4,447,541 to Peterson which discusses various methods for biological decomposition of polyhalogenated organic compounds (PCB's) by treatment with microorganisms of the Pseudomonas type under special conditions of soil pH.
U.S. Pat. No. 4,452,894 to Olsen et al and No. 4,385,121 to Knowlton also disclose the degradation of hydrocarbons and halogenated aromatic hydrocarbons, respectively, using aerobic methods.
A substantial problem in this area is the contamination of drinking water by halogenated hydrocarbons which heretofore appeared non-biodegradable. Compounds such as trichloroethylene, tetrachloroethylene, carbon tetrachloride, 1,1,1-trichloroethane, vinyl chloride, 1,2-dichloroethane, and the like are especially difficult to remove from water. The extent of contamination in industrial regions is suggested from a survey of the State of New Jersey (Tucker, "Groundwater Quality in New Jersey: an Investigation of Toxic Contaminants"; Available from Office of Cancer and Toxic Substances Research, New Jersey Department of Environmental Protection). This study showed that more than a quarter of the wells sampled contained detectable concentrations of halogenated aliphatic compounds, a tenth had concentrations in excess of 10 ug/l, and one to two percent had concentrations in excess of 100 ug/l. The "Safe Drinking Water Act" (42 USC 300) requires the Environmental Protection Agency to establish primary drinking water regulations. One of the aspects of these regulations is to establish a maximum contamination level of halogenated organic materials such as those mentioned above. Proposed rules for drinking water regulations were published in the Federal Register, Volume 49, No. 114, 24329-24355, June 12, 1984.
The proposed Recommended Maximum Contaminant Levels (RMCL's) are zero for trichloroethylene, tetrachloroethylene, and carbon tetrachloride, and 200 ug/l for 1,1,1-trichloroethane.
Substantial work has been carried out to determine the levels of contaminants of this type, together with attempts as to how such contaminants may be removed. For example, Parsons et al, J. Am. Water Works Assoc., Vol. 76 (2), February 1984, pages 56-59, studied the contamination of drinking water by trichloroethene, which is a compound used as a drycleaning solvent. Wilson et al, J. Environ. Qual., Volume 10, No. 4, pages 501-506, 1981, discusses a study of the vulnerability of ground waters to pollution by organic chemicals that migrate through the soil, including various halogenated hydrocarbons. This article concluded that most low molecular weight halogenated aliphatic hydrocarbons were transported readily through the soil, which explained the increasingly frequent occurrence of these compounds in ground water.
In a publication by Wilson et al, EOS, Vol. 64, No. 33, page 505, Aug. 16, 1983, the authors studied the biological transformation of organic pollutants in ground water, and particularly the biotransformations of organic pollutants in the deeper subsurface environment. It was concluded that the rate of transformation is limited by the numbers and activity of microorganisms available, while the extent of transformation is most frequently limited by some requirement for metabolism such as oxygen, pH buffering capacity or mineral nutrients. In Table 2 of this publication the authors also set forth their opinion as to prospects for biotransformation of several important classes of organic pollutants found in ground water. The predictions were based on a cautious extrapolation from the behavior of the compounds and other natural systems. In general, the authors concluded as may be noted from Table 2 of that publication that for many halogenated aliphatic hydrocarbons there was no prospect of biotransformation in water table aquifers.
A further study was reported by Wilson et al, In Giuliano Ziglio, page 183-195, 1983, Monduzzi Editorie SPA, Bologna, Italy, wherein it was reported that, in general, halogenated aliphatic hydrocarbons are resistent to biodegradation in aerobic subsurface environments and this contributes to their persistence in polluted ground waters.
In a publication by Love et al, J. Am. Water Works Assoc., Vol. 74, August 1982, pages 413-425, there is set forth the results of studies on laboratory and pilot scales to ascertain the effects of aeration, adsorption and boiling for the removal of volatile organic solvents from water. None of these methods appear to be satisfactory for the removal of certain of these volatile materials.
Other work has included qualitative and quantitative studies with respect to the amount of volatile organic compounds of this type which may be contained in the soil or in the water. For example, in a publication by Bellar et al, J. Am. Water Works Assoc., Vol. 66, December, 1974, pages 739-744, the authors describe a method for the quantitative recovery of volatile organic compounds including chlorinated organic solvents from waste water using gas chromatographic procedures.
Studies have also been carried out with respect to possible transformation of halogenated aliphatic compounds using various bacteria. For example, in a publication by Bouwer et al, Appl. Environ. Microbiol., Volume 45, (4), pages 1286-1294, April, 1983, the transformation of 1- and 2-carbon halogenated aliphatic organic compounds was studied under methanogenic conditions. These authors concluded that several 1- and 2-carbon halogenated aliphatic organic compounds which were present at low concentrations in ground water were degraded under methanogenic conditions in batch baterial cultures and in a continuous flow methanogenic fixed film laboratory scale column. The authors suggest that transformation of halogented aliphatic compounds can occur under methanogenic conditions in the environment, but it was their conclusion that degradation of halogenated aliphatic compounds did not occur under the aerobic conditions of the study.
Many studies have been made with respect to bacteria contained in water of various types. Thus, in a publication by Wilson et al, Ground Water, Volume 21, No. 2, March-April, 1983, pages 134-142, the authors studied the enumeration and characterization of bacteria which are indigenous to a shallow water table aquifer. The goal of this study was simply to determine the bacteria present in such environments. In these studies concentrations of various halogenated organic volatile materials were determined and their degradation by bacteria contained in water table aquifers were then measured. The conclusions were that certain materials were degraded slowly and others were not degraded at all. For example, there was no detectable degradation of 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene or tetrachloroethylene. A similar report is described by Wilson et al in Developments of Industrial Microbiology, Vol. 24, p. 225-233 (1983).
In none of the prior art of which Applicants are aware are there successful procedures for degradation of certain low molecular weight halogenated aliphatic hydrocarbons, and particularly unsaturated chlorinated hydrocarbons under aerobic conditions. The present invention provides a solution to this problem.